In a standard shuttleless loom a weft yarn is pulled from a supply spool by a mechanical feeder and fed through a fixed-resistance mechanical brake to a nozzle that is directed crosswise through a shed formed between upper and lower sheds of warp yarns. Inside the shed the yarn is guided along a passage formed by the teeth of a confining comb mounted on a support along with the beating comb. The yarn is moved the entire weft-wise width of the fabric by relay nozzles spaced along the shed and pressurized sequentially. At the downstream edge of the goods the yarn is trapped by a weft-yarn aspirator and held thereby. Such an arrangement is described in French patents Nos. 2,184,052, 2,448,293, and 2,526,053.
The aspirator operates pneumatically like the relay nozzles and insertion nozzle and sucks in the weft filament. It normally is formed by a tube aligned with the insertion nozzle and equipped with an internal air jet directed away from the insertion nozzle so that by venturi or jet-pump effect it creates suction at the intake end of the tube. The downstream flow of air away from the insertion nozzle not only pulls in the weft filament but maintains it under some tension once it is aspirated. The function of this holder, whose intake jet is pressurized sequentially after the last of the relay nozzles to economize compressed gas, is to position and then maintain some tension in the weft yarn during beating in. Unfortunately this system not only is quite wasteful of compressed gas but also is often not able to maintain enough tension in the weft yarn. What is more it relies on the relay nozzles for the holding effect so that gas is wasted in this manner also.